Remove gitter badge from README.md

There has not been activity there for several years. No point in
actively inviting potential using developers in there, instead of
just using what we have on GitHub.

README.md

@@ -2,7 +2,7 @@
 
 > What could be more logical awesome than no logic at all?
 
-[![Build Status](https://travis-ci.org/janl/mustache.js.svg?branch=master)](https://travis-ci.org/janl/mustache.js) [![Gitter chat](https://badges.gitter.im/Join%20Chat.svg)](https://gitter.im/janl/mustache.js)
+[![Build Status](https://travis-ci.org/janl/mustache.js.svg?branch=master)](https://travis-ci.org/janl/mustache.js)
 
 [mustache.js](http://github.com/janl/mustache.js) is a zero-dependency implementation of the [mustache](http://mustache.github.com/) template system in JavaScript.